Aluminum base for electric lamps having a plastic coating for improved corrosion resistance

Abstract

A screw base for high intensity discharge lamps or for larger sizes of incandescent lamps utilizes a threaded aluminum shell coated with a thin film of polytetrafluoroethylene. The thin film is penetrated at points of maximum contact pressure with the socket to provide electrical continuity while effecting a low friction surface preventing galling and sticking of the base in the socket and permitting easy lamp insertion and removal.

What we claim as new and desire to secure by Letters Patent of the United States is: 
     
       1. A screw base for an electric lamp of the kind comprising a threaded metal shell and a center contact mounted on an insulator uniting it to the shell, said shell being of aluminum coated externally with a thin self-adherent layer of soft protective plastic material having lubricative properties and a coefficient of friction less than 0.1, said layer being penetrable at points of maximum contact pressure when screwed into a socket in order to provide circuit continuity, said layer otherwise remaining in place to provide protection against corrosion of the aluminum and serving as a lubricant for easy lamp removal from the socket. 
     
     
       2. A base as in claim 1 wherein the plastic material is a polymeric fluorocarbon. 
     
     
       3. A base as in claim 1 wherein the plastic material is polytetrafluoroethylene. 
     
     
       4. A base as in claim 1 where the plastic material is polyphenylene sulfide. 
     
     
       5. A base as in claim 1 wherein the plastic material is polytetrafluoroethylene in a thickness of at least 0.0005'. 
     
     
       6. A base as in claim 1 wherein the plastic material is a polymeric fluorocarbon containing a filler of graphite or carbon black. 
     
     
       7. A base as in claim 1 wherein the plastic material is polytetrafluoroethylene in a thickness from approximately 0.0005" to 0.0015" and containing graphite or carbon black as a filler.